Aim. To study biological (cell and anticytokine) therapy-induced changes in the levels of proinflammatory cytokines in patients with inflammatory bowel diseases (IBD). Subjects and methods. Forty-four patients with chronic continuous or chronic recurrent IBD were examined. According to the performed therapy, the patients were divided into 3 groups: 1) 16 patients who took infliximab; 2) 14 patients who received combination anti-inflammatory therapy with the cultured mesenchymal stromal cells (MSC) being administered; 3) 14 patients who had standard anti-inflammatory therapy with 5-aminosalycilic acid preparations and glucocorticosteroids. The concentrations of tumor necrosis factor-α (TNF-α), interferon-γ (INF-γ), and interleukins (IL)-2, -5, -8, -12, and -15 were determined in the patients' sera before and 2 months after therapy initiation. Results. The elevation in the serum levels of the proinflammatory cytokines TNF-α, INF-γ, and IL-2, -5, -8, -12, and -15 indicates their implication in the pathogenesis of ulcerative colitis and Crohn's disease. Their levels may evaluate both the activity of an inflammatory process and the efficiency of the therapy. The higher level of these cytokines is accompanied by the enhanced activity of diseases, which may be used to diagnose their activity, to predict the course of IBD, and to perform adequate therapy. The decreased level of the proinflammatory cytokines is indicative of the efficiency of the therapy in patients with IBD. Conclusion. By reducing TNF-α levels, infliximab therapy results in a decrease in the concentrations of other proinflammatory cytokines (IL-1, -2, -5, -8), thus lowering the inflammatory activity of IBD. MSC transplantation also reduces the level of most proinflammatory cytokines, thus diminishing the intensity of immunopathological processes, which is shown by positive changes in the clinical picture of the disease.